CALIFORNIA 
AGRICULTURAL  EXTENSION  SERVICE 

CIRCULAR  14 

September,  1927 


SELECTION  AND  CARE  OF  ELECTRICAL 

EQUIPMENT  USED  IN  DAIRY 

MANUFACTURING 


A.  W.  FARRALL 


PUBLISHED  BY 

THE  COLLEGE  OF  AGRICULTURE 
UNIVERSITY  OF  AGRICULTURE 


Cooperative  Extension  work  in  Agriculture  and  Home  Economics,  College  of  Agriculture, 
University  of  California,  and  United  States  Department  of  Agriculture  cooperating.  Dis- 
tributed in  furtherance  of  the  Acts  of  Congress  of  May  8  and  June  30,  1914.  B.  H.  Crocheron, 
Director,  California  Agricultural  Extension  Service. 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1927 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/selectioncareofe14farr 


SELECTION  AND  CARE  OF  ELECTRICAL 

EQUIPMENT  USED  IN  DAIRY 

MANUFACTURING 

A.  W.  FAKRALLi 


The  use  of  electrical  energy  has  become  general  in  California.  A 
recent  questionnaire  survey,  conducted  by  the  author,  showed  that 
more  than  92  per  cent  of  the  900  dairy  manufacturing  plants  of  Cali- 
fornia use  electricity  for  power.  It  is  also  estimated  that  65  per  cent 
of  the  farms  of  California  use  some  type  of  electrical  equipment.2  In 
addition,  there  are  a  large  number  of  dehydraters,  preserving  fac- 
tories, and  canning  works,  which  use  electrical  machinery. 

A  demand  has  arisen  from  many  of  these  sources,  particularly 
from  the  dairy  manufacturing  plants,  for  more  information  regarding 
the  selection,  care,  and  operation  of  electrical  equipment,  as  applied  to 
dairy  conditions.  In  order  to  provide  this  information  and  thereby 
assist  the  operator  in  making  the  most  efficient  use  of  his  equipment, 
this  publication  has  been  prepared.  Much  of  the  data  were  collected 
from  the  viewpoint  of  dairy  manufacturing,  but  applications  may 
easily  be  made  to  cover  conditions  in  general  agriculture,  such  as 
pumping,  lighting,  and  other  general  purposes. 


DEFINITION    OF    ELECTRICAL    TERMS 

A  knowledge  of  the  meaning  of  the  terms  which  are  in  frequent 
use  in  connection  with  electrical  equipment,  is  necessary  for  the 
understanding  of  this  publication. 

Voltage  is  the  term  which  applies  to  the  electrical  pressure  in  a 
system.  The  direction  of  flow  of  current  is  always  from  a  point  of 
high  to  one  of  low  pressure.  The  terminals  of  a  generator  or  battery 
might  be  thought  of  as  the  high  and  low  pressure  points.  If  no  volt- 
age is  present  no  energy  will  flow,  or  if  the  electrical  pressure  is  the 
same  for  both  terminals  no  current  will  flow.  Lowering  of  the  voltage 
causes  a  reduced  current  flow  in  a  system  and  raising  it  causes  an 


1  Junior  Agricultural  Engineer  in  the  Experiment  Station,  Division  of  Dairy 
Industry  and  Agricultural  Engineering  Cooperating. 

2  Data  from  Committee  on  the  Relation  of  Electricity  to  Agriculture. 


4  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [ClRC.  14 

increased  flow.  Electrical  equipment  is  made  to  operate  on  a  given 
voltage,  which  should  be  used  to  secure  best  results.  Ordinary  com- 
mercial voltages  are  110  volts  for  lighting  and  220  volts  for  power, 
although  in  the  larger  power  units,  440  or  even  2200  are  used. 

A  given  amount  of  energy  may  be  transmitted  over  a  high  voltage 
system  with  less  loss  than  when  low  voltages  are  used.    Thus  if  a  motor 

draws  1100  watts  from  the  line,  it  will  require  =  5  amperes 

of  current  when  used  as  a  220-volt  line.     If  it  is  used  on  a  110-volt 

line  the  amperage  will  be  — 10  amperes.     The  loss  in  energy 

through  a  line  having  3  ohms  resistance  will  be  52  X  3  =  75  watts  in 
the  case  of  the  220-volt  line,  while  on  the  110-volt  line  it  will  be 
102  X  3  =  300  watts.  There  is  a  further  advantage  in  using  the 
higher  voltage  when  possible  in  that  the  drop  in  voltage  when  using 
a  given  size  of  wire  for  a  given  load,  is  less  than  when  a  low  voltage 


Fig.  1. — Voltmeter  for  measuring  electrical  pressure.  The  illustration  also 
shows'  a  trouble  lamp,  which  can  be  used  instead  of  a  voltmeter  to  determine 
pressure,  although  not  accurately. 

is  used.  Many  instances  are  on  record  where  a  motor  which  was 
situated  some  distance  from  the  transformer  did  not  operate  satisfac- 
torily on  110  volts,  but  did  when  the  line  and  motor  were  changed  to 
operate  at  220  volts. 

Voltage  may  be  measured  by  means  of  a  voltmeter  (fig.  1)  which 
is  connected  directly  across  the  circuit.  A  trouble  lamp  (fig.  1) 
equipped  with  a  220-volt  lamp  may  also  be  used  for  determining  volt- 
ages, roughly.  If  the  lamp  shines  bright,  the  line  voltage  is  probably 
220  volts,  while  if  it  shows  dim,  it  is  very  likely  110  volts. 

Amperage  refers  to  the  rate  of  flow  of  a  current  of  electricity. 
One  ampere  is  the  amount  of  current  which  will  be  forced  through  a 
resistance  of  one  ohm  by  a  pressure  of  one  volt.  The  amperage 
requirement  of  a  circuit  is  important  mainly  because  it  determines  the 


1927]        ELECTRICAL  EQUIPMENT   USED  IN   DAIRY   MANUFACTURING  5 

size  of  wires  and  the  size  of  fuses  which  must  be  used.  A  large  wire 
should  be  used  for  carrying  a  large  current.  Table  1  shows  the  allow- 
able carrying  capacity  of  various  sizes  of  copper  wire,  according  to  the 
National  Board  of  Fire  Underwriters. 

The  watt  is  the  unit  for  the  measurement  of  electrical  power. 
One  horsepower  is  equivalent  to  746  watts.  The  kilowatt  (abbreviated 
kw.,  or  K.W.)  equals  1000  watts. 


TABLE  1 

Allowable  Carrying  Capacity  of  Wires 


B.  &  S.  gage 

Rubber  insulation 

Varnished  cloth  insulation 

Other  insulation 

18 

Amperes 

3 

Amperes 

Amperes 

5 

16 

6 

10 

14 

15 

18 

20 

12 

20 

25 

25 

10 

25 

30 

30 

8 

35 

40 

50 

6 

50 

60 

70 

5 

55 

65 

80 

4 

70 

85 

90 

3 

80 

95 

100 

2 

90 

110 

125 

1 

100 

120 

150 

0 

125 

150 

200 

00 

150 

180 

225 

000 

175 

210 

275 

200 

240 

300 

0000 

225 

270 

325 

The  kilowatt-hour  (kw-hr.)  is  the  standard  commercial  unit  for 
measurement  of  electrical  energy,  commonly  spoken  of  as  "power," 
although  incorrectly.  It  represents  the  amount  of  energy  expended  by 
1000  watts  flowing  for  one  hour,  or  say  500  watts  flowing  for  two 
hours.    Kilowatt-hours  equal  kilowatts  times  hours. 

Direct  current  flows  always  in  the  same  direction,  as  from  the 
poles  of  a  dry  battery. 

Alternating  current  (A.C.)  flows  first  in  one  direction  and  then 
in  the  other.  It  starts  from  zero  and  gradually  builds  up  to  the 
maximum  voltage,  flowing  in  one  direction;  then  it  decreases  in 
strength  down  to  zero  and  builds  up  to  a  maximum  voltage,  flowing 
in  the  opposite  direction,  after  which  it  gradually  decreases  in  strength 
until  it  again  reaches  zero  value.  This  complete  set  of  changes  is 
called  a  cycle.     Standard  alternating  current  makes  60  of  these  com- 


CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE 


[Cmc.  14 


plete  cycles  every  second  and  is  therefore  called  60-cycle  current. 
Alternating  current  is  used  largely  today,  because  its  voltage  may  be 
easily  changed  by  means  of  transformers,  enabling  it  to  be  carried 
long  distances  at  high  voltage  with  small  loss. 

The  phase  of  an  alternating  current  circuit  is  important  since  it 
determines  the  type  of  motor  used,  and  the  general  wiring  scheme. 
One,  two  and  three-phase  systems  are  the  most  common  types.  One 
might  consider  phase  as  meaning  circuit.  In  a  single-phase  system, 
there  is  just  one  main  circuit  or  path  in  which  the  current  can  travel 
to  the  generator  and  back,  while  in  a  three-phase  there  are  three 


Ll     L2    L3 


LI     L2 


6 
A 


3-Phase        Single-Phase 

Fig.  2. — A  three-phase  system  has  three  separate  circuits  acting  as  a  unit, 
while  the  single  phase  has  only  one.  Ll,  L2,  and  L3  indicate  conductors.  Loads 
may  be  placed  at  points  A,  B,  and  C. 

primary  circuits,  and  the  main  current  surge  is  in  each  one  suc- 
cessively. The  sum  of  the  currents  in  any  two  circuits  at  a  given 
instant  is  equal  and  opposite  that  in  the  other  one.  If  one  lead  wire  is 
broken  it  immediately  kills  two  phases  leaving  only  one  still  operating 
at  full  capacity.  This  is  known  as  "single-phasing."  This  is  what 
happens  after  one  fuse  of  a  3-phase  motor  has  burned  out.  Single- 
phase  current  may  be  obtained  by  "tapping  into"  any  two  wires  of 
a  3-phase  system.  Three-phase  systems  are  very  generally  used  for 
power  circuits,  because  the  energy  can  be  transmitted  more  economic- 
ally, and  also  because  the  rugged  3-phase  induction  motors  may  be 
used. 


I927]        ELECTRICAL  EQUIPMENT   USED  IN  DAIRY   MANUFACTURING  7 

Single-phase  current  is  used  for  lighting  and  for  small  power 
circuits.    Figure  2  illustrates  the  two  systems. 

Power  factor  is  defined  as  the  ratio  of  the  watts  (which  is  the 
measure  of  true  power  being  used)  to  the  product  of  volts  and 
amperes.  Thus  if  in  a  circuit,  a  wattmeter  read  6000  watts,  while 
a  voltmeter  read  220  and  an  ammeter  30,  the  power  factor  would  be 

=  90  per  cent.     The  most  economical  power  factor  is  unity 

or  100  per  cent,  since  the  lower  the  power  factor,  the  larger  the  cur- 
rent that  must  be  handled  by  motors  and  wires  in  order  to  develop  a 
certain  power.  Low  power  factor  results  in  heating  of  motors,  voltage 
drop  and  loss  of  energy.  It  is  to  the  interest  of  a  plant  owner,  to  keep 
the  power  factor  as  near  unity  as  possible.  The  principal  cause  of 
low  power  factor  is  operation  of  induction  motors  at  light  load. 
Synchronous  motors  have  the  ability  to  raise  the  power  factor  of  a 
system,  and  are  often  employed  with  this  purpose  in  mind. 


TYPES    OF    MOTORS    AND    THEIR    OPERATION 

Types  of  Motors. — The  motors  most  commonly  used  in  dairy  manu- 
facturing plants  are  of  five  general  types,  as  follows : 

The  single-phase  motors  are  generally  used  in  the  smaller  sizes, 
below  one-half  horsepower,  because  of  the  ease  with  which  they  may 
be  connected  to  the  line.  They  are  also  used  in  some  places  in  larger 
sizes,  where  3-phase  current  is  not  available.  They  are  usually  heavier 
and  more  expensive  for  their  power  than  3-phase  motors.  They  are 
also  slightly  less  efficient  and  are  more  difficult  to  protect  from 
moisture. 

The  repulsion-induction  single-phase  motor  uses  a  wound  rotor 
and  lias  a  commutator  and  brushes.  These  must  be  kept  well  fitted, 
clean,  and  properly  adjusted  or  they  will  cause  sparking,  especially 
during  the  starting  period.  This  type  of  motor  has  a  good  starting 
torque,  and  is  used  on  many  iceless  ice  cream  cabinets. 

The  split-phase  motor,  in  addition  to  the  regular  armature  wind- 
ing, employs  a  small  starting  winding  of  high-resistance  wire,  which 
is  in  operation  during  the  starting  period  and  which  is  thrown  out 
of  service  by  a  centrifugally  operated  switch  after  the  motor  has 
reached  its  normal  speed.  This  type  of  motor  does  not  ordinarily 
have  as  good  starting  torque  as  the  repulsion-induction  type. 

The  3-phase  squirrel-cage  motor  as  usually  constructed,  consists 
of  a  stationary  part  called  the  stator,  which  holds  the  windings  and 


8  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [ClEC.  14 

supports  the  bearings,  and  a  rotating  part  in  which  the  conductors 
are  a  series  of  copper  or  aluminum  bars.  These  are  welded  or  cast 
together  in  the  shape  of  the  traditional  squirrel  cage,  hence  the  name. 
This  type  of  motor  is  simple,  rugged  and  very  efficient,  is  easily  water- 
proofed, and  has  practically  constant  speed  under  varying  loads.  For 
these  reasons,  it  has  become  very  popular  and  has  given  good  satis- 
faction in  actual  use.  The  parts  of  this  type  are  shown  in  figure  3, 
unassembled. 

The  double-wound  squirrel-cage  motor  is  a  new  development,  which 
allows  the  motor  to  be  started  directly  on  the  line,  in  sizes  up  to  50 
horsepower  without  the  use  of  a  starting  compensator. 

The  3-phase  wound-rotor  type  motor  has  windings  in  the  rotor  as 
well  as  on  the  stator,  and  ordinarily  uses  brushes  and  slip  rings.  It 
has  the  ability  to  start  a  heavier  load  with  less  voltage  disturbance  on 
the  line  than  the  squirrel-cage  type ;  for  this  reason,  it  is  used  where 
it  is  necessary  to  start  a  very  heavy  load  frequently.  A  further  advan- 
tage of  this  motor  is  that  its  speed  can  be  varied  considerably  by  means 
of  a  special  type  of  controller.  The  disadvantages  are  that  it  is  not 
quite  as  efficient  as  the  squirrel-cage  type,  that  it  is  not  as  strong 
mechanically  or  electrically,  that  it  requires  more  upkeep,  and  that  it 
cannot  easily  be  made  water  proof. 

The  synchronous  motor  is  so  constructed  that  it  operates  at  con- 
stant speed  at  all  loads.  It  has  the  ability,  if  properly  adjusted,  to 
increase  the  power  factor  of  the  line.  Since  an  auxiliary  direct  cur- 
rent exciter  must  be  used  in  conjunction  with  this  motor,  it  is  custom- 
ary to  use  it  only  in  the  larger  sizes.  It  is  often  used  for  driving 
refrigeration  machinery. 

Characteristics  of  Motors. — Every  motor  has  certain  individual 
characteristics  which  are  typical  of  its  action.  Some  of  these  are  start- 
ing ability,  speed,  torque,  power  factor,  heating,  and  capacity  for 
doing  work. 

The  starting  characteristics  of  a  motor  are  dependent  upon  the 
design,  but  all  are  similar  in  that  they  draw  a  very  heavy  current  from 
the  line  at  this  period  of  their  operation.  A  large  motor,  if  thrown 
directly  upon  the  line,  may  cause  a  serious  drop  in  voltage,  flickering 
of  lights,  or  even  burning  out  of  fuses.  Motor  starters,  which  reduce 
the  starting  voltage,  are  sometimes  used  in  order  to  overcome  these 
troubles.  Double  wound  squirrel-cage  type  motors  have  recently  been 
developed,  which  are  greatly  improved  in  this  respect,  and  may  be 
thrown  directly  upon  the  line  without  serious  effect. 


J 927 J        ELECTRICAL  EQUIPMENT  USED  IN   DAIRY   MANUFACTURING 


Reference 

Letter  Description 

A  Stator,  complete.  Give  Spec.  No.  of 
stator  coil  stamped  on  part  number 
name  plate. 

B  Stator  spider  without  punchings,  wind- 
ings, and  terminal  board. 

C  Stator  coil.  Give  Spec.  No.  stamped  on 
part  number  name  plate. 

D      Set  of  stator  punchings. 

E       Stator  end  connection. 

F       Stator  flange. 

G       Stator  wedge. 

H      Terminal  board,  complete. 

I        Terminal  board. 

J        Terminal  for  terminal  board  lead. 

K       Terminal  lead. 

L       Cap  screw  for  terminal  board. 

M      Terminal  bushing. 

N      Bolt  and  nut  for  terminal. 

O       Outside  space  block. 

P       End  shield. 

Q       Bolt  fastening  end  shield  to  stator. 

R      Dust  guard. 

S       Pipe  plug  for  end  shield. 

T       Drain  plug  for  end  shield. 

U       Oil  gauge,  complete. 

V       Cap  for  oil  gauge. 


Reference 

Letter  Description 

W  Nipple  for  oil  gauge. 

X  Elbow  for  oil  gauge. 

Y  Bearing  lining.     Give  Cat.   No.   stamped 
on  part  number  name  plate. 

Z  Oil  ring. 

Aa  Set  screw  for  bearing  lining. 

Ba  Oil  well  cover,  complete. 

Ca  Screw  for  oil  well  cover. 

Da  Sliding  Base,  complete. 

Ea  Belt  tightener  carrier. 

Fa  Belt  tightener  screw. 

Ga  Base  clamp. 

Ha  Guide  washer  for  sliding  bar. 

la  Bolt  fastening  stator  to  sliding  bar. 

Ja  Nut  for  la. 

Ka  Sleeve  for  belt  tightener  screw. 

La  Nut  for  belt  tightener  screw. 

Ma  Rotor,  complete. 

Na  Shaft,  bare. 

Oa  Fan 

Pa  Cap  screw  fastening  fan  to  flange. 

Qa  Lock  washer  for  Pa. 

Ra  Key  for  pulley. 

Sa  Pulley. 

Ta  Name  plate. 

Ua  Conduit  terminal  box,  complete. 


Fig. 


3. — Parts  of  a  three-phase  squirrel-cage  type  motor, 
of  General  Electric  Co.) 


(Courtesy 


10  CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE  [ClRC.  14 

The  torque  (tork),  or  turning  effort  of  a  motor,  is  its  ability  to 
rotate  its  shaft.  This  ability  is  greater  on  a  1200  R.P.M.  motor  than 
on  an  1800  R.P.M.  motor  of  the  same  horsepower.  It  is  measured  in 
pound-feet  and  is  illustrated  as  follows :  If  a  motor  has  a  torque  of 
10  pound-feet,  it  has  the  ability  to  exert  a  pull  of  10  pounds  on  the 
rim  of  a  pulley  which  is  one  foot  from  the  center  of  the  shaft,  or 
5  pounds  on  the  rim  of  a  pulley  which  is  2  feet  from  the  center. 

The  starting  torque  varies  with  the  type  of  motor.  This  point 
should  be  given  special  consideration  in  some  types  of  service,  as  for 
example,  that  of  starting  a  heavy  refrigeration  machine.  With  single- 
phase,  repulsion-induction  motors,  the  setting  of  the  brushes  greatly 
affects  the  starting  torque. 

The  pull-out  torque  is  the  point  at  which  the  motor  will  stop  on 
account  of  too  great  a  load,  and  is  usually  from  two  to  three  times  the 
normal  full-load  torque.  Low  voltage  causes  a  considerable  decrease 
in  torque. 

The  speed  of  an  alternating  current  induction  motor  is  deter- 
mined by  the  number  of  poles  it  has,  and  by  the  frequency  or  cycles 
per  second  of  the  circuit  on  which  it  is  used.    A  four-pole  motor  on  a 

60-cycle  circuit  has  a  synchronous  speed  of =1800  R.P.M. 

-^  i    ^  -r^  ™       120  X  frequency 

Formula  R.P.M.  = ^ § — r^- 

number  or  poles 

The  speed  of  an  alternating-current  motor  may  be  changed  by 
reconnecting  the  windings  so  that  there  are  a  different  number  of 
poles,  or  by  placing  it  on  a  line  of  different  frequency.  If  a  60-cycle 
motor  of  1200  R.P.M.  is  operated  on  a  50-cycle  circuit,  its  speed  will 
be  reduced  to  approximately  five-sixths  of  its  rated  speed. 

The  R.P.M.  of  variable  speed  alternating-current  induction  motors 
is  changed  by  means  of  a  controller,  which  shifts  the  connections, 
making  a  different  number  of  poles. 

The  power  factor  of  a  motor  is  affected  very  largely  by  its  size 
and  design  and  by  the  load  carried.  A  well  loaded  motor  usually  has 
a  good  power  factor,  while  one  carrying  only  a  quarter  load,  for 
example,  has  a  low  power  factor.  This  causes  a  lowering  of  the  power 
factor  on  the  whole  electrical  system  and  may  result  in  overheating 
the  other  motors  on  the  line.  Large  motors,  as  a  rule,  have  a  higher 
power  factor  than  small  ones.  Overloads  cause  low  power  factor 
similar  to  underloads. 

Heating  of  motors  is  a  subject  of  great  importance,  because  it  is 
most  often  the  first  sign  of  trouble,  and  because  it  is  also  the  factor 
which  determines  the  safe  limit  of  load  that  a  motor  will  carry. 


I927]        ELECTRICAL  EQUIPMENT   USED  IN   DAIRY   MANUFACTURING  11 

Motors  are  rated  as  40  degree  and  50  degree  motors,  meaning  that 
they  will  develop  their  rated  horsepower  continuously,  with  a  tem- 
perature rise  of  not  more  than  the  respective  number  of  degrees  centi- 
grade above  atmospheric  temperature.  1°  Centigrade  equals  1.8° 
Fahrenheit.  If  a  40°  motor  is  operated  in  an  atmosphere  of  70°  F 
the  maximum  temperature  of  its  windings  should  not  exceed  [40  X 
1.8]  -f-  70  =  142°  F.  Under  similar  conditions,  50°  motor  would 
have  a  temperature  not  exceeding  160°  F.  A  40°  motor  is  generally 
built  larger  or  with  a  better  ventilating  system  than  a  50°  motor,  and 
in  general,  it  has  a  greater  overload  capacity.  The  proper  ventilation 
of  motors  is  of  great  importance  in  keeping  them  from  overheating. 
All  hoods  or  covers  should  be  ventilated. 

Any  localized  heating  of  the  motor  is  usually  a  sign  of  trouble  and 
should  be  looked  after  immediately.  A  rough  method  of  determining 
when  a  motor  is  overheated  is  as  follows :  If  the  hand  cannot  be  held 
on  the  motor  winding  or  stator  for  twenty  seconds,  the  motor  is  too 
hot.  A  more  accurate  method  is  to  place  the  bulb  of  an  ordinary 
thermometer  down  into  the  stator  winding  against  the  coils  and  read 
the  maximum  temperature. 

Low  power  factor,  overloading,  poor  ventilation,  low  voltage,  and 
defective  windings  are  frequent  causes  of  overheating. 

Determining  the  Load  for  Motors. — Proper  loading  of  motors  is 
one  of  the  greatest  factors  in  their  economical  and  successful  use. 
Overloading  is  expensive  and  dangerous,  because  of  likelihood  of  burn- 
ing out  the  motor  windings.  Underloading  is  expensive  because  of 
greater  first  cost  of  equipment,  such  as  motor,  wire,  and  switches,  and 
because  of  lower  efficiency  of  the  motor.  With  many  motors,  a  differ- 
ence of  from  4  to  8  per  cent  in  efficiency  is  found  between  full  and 
half  load.     Smaller  loads  result  in  much  lower  efficiency. 

The  average  motor  has  the  ability  to  carry  momentary  overloads 
of  100  per  cent  without  injury.  The  limit  of  load  is  really  deter- 
mined by  the  heating  of  the  motor.  In  a  system  in  which  there  is  low 
power  factor,  or  low  voltage,  a  motor  will  not  carry  as  great  a  load 
as  under  normal  conditions.  Motors  operating  in  warm  places  or 
where  ventilation  is  poor,  are  also  limited  in  the  load  they  may  safely 
carry. 

It  is  the  average  load,  such  as  is  shown  in  figure  4  and  not  the  peak 
load,  which  determines  the  heating  of  the  motor,  and  therefore,  the 
amount  that  may  be  safely  carried,  provided  that  it  is  not  large 
enough  to  stall  the  motor  at  the  peak  load. 


12 


CALIFORNIA    AGRICULTURAL    EXTENSION    SERVICE 


[CIRC.  14 


In  all  cases  where  there  is  doubt,  it  is  advisable  to  check  the  actual 
requirements  of  a  machine  before  determining  the  size  of  motor  to  buy. 
It  is  always  better  to  use  a  motor  that  is  too  large  rather  than  one  that 
is  too  small. 

Protection  from  Moisture. — Moisture  has  been  called  the  greatest 
enemy  of  electricity.  This  is  especially  true  in  creamery  work.  Since 
water  is  a  good  conductor  of  electricity,  its  presence  causes  shorts  or 


3 
0 

—  «—«—« 

^^^^™«— ■ — 

—J* 

P«BMM>M»^d 

^.          ~"^^~"" 

—                               —  — 

CL 
CD 

Maximum    load 

O 

X 

1 

Average  load 

0 


4  6 

Minutes 


Q 


10 


Fig.  4. — The  average  load  and  not  the  peak  load  usually  determines  the  heating, 
and  therefore,  the  size  of  motor  which  must  be  used. 


grounds  in  electrical  equipment,  and  careful  attention  should  be  given 
to  avoid  these  difficulties.  It  is  impossible  to  make  the  ordinary  open 
type  motor  entirely  waterproof,  although  many  3-phase  motors  will 
withstand  considerable  moisture.  It  is  advisable  to  use  hoods  or 
shields  over  motors  and  other  electrical  equipment.  A  good  type  of 
hood  is  shown  in  figure  5.  This  hood  allows  ventilation,  which  is  very 
important,  in  keeping  the  motor  cool. 

There  are  motors  built  which  have  especially  protected  windings 
enclosed  in  a  waterproof  substance.  Some  of  these  are  giving  very 
good  service  under  actual  commercial  conditions. 

Motors  completely  enclosed  are  sometimes  used,  but  the  special 
problem  with  them  is  that  of  overheating.  This  type  of  motor  is 
sometimes  connected  to  an  external  ventilating  system  and  is  thus 
kept  cool. 


I927]        ELECTRICAL  EQUIPMENT   USED  IN  DAIRY   MANUFACTURING  13 

The  location  of  the  motor  on  a  raised  block,  or  in  a  place  where  it 
will  not  be  subject  to  contact  with  streams  of  water,  will  prevent  much 
trouble  from  moisture. 

It  is  good  policy  to  dry  motors  thoroughly  once  a  year,  and  then 
spray  them  with  a  good  insulating  and  waterproof  paint,  being  par- 
ticularly careful  to  cover  the  windings.  Sometimes  a  waterproof 
putty  is  used  to  cover  the  windings,  but  with  this  material,  care  must 
be  taken  not  to  close  too  many  air  passages,  and  thus  effect  poor 
ventilation  and  consequent  overheating  of  the  motor. 

Selection  of  Motors. — In  the  selection  of  motors  a  number  of 
features  should  be  given  special  attention.  Perhaps  the  first  of  these 
should  be  selection  of  a  motor  of  proper  size,  i.e.,  one  which  will  handle 
the  load  under  all  normal  conditions,  and  one  which  has  sufficient 
starting  torque  to  bring  the  load  up  to  speed  quickly. 

The  second  consideration  should  be  that  of  ruggedness  and 
reliability.  A  motor  should  be  of  as  simple  construction  as  possible 
and  should  have  great  mechanical  and  electrical  strength.  The  3-phase 
squirrel-cage  type  of  motor  is  an  example  of  a  strong,  rugged  con- 


Fig.  5. — Ventilated  motor  hood,  for  protection  of  motor.     Ventilator  near  top 
of  hood  allows  circulation  of  air  about  the  motor. 

struction,  in  which  there  are  no  delicate  parts  to  break  or  get  out  of 
adjustment. 

Its  ability  to  resist  moisture,  if  the  motor  is  to  be  subject  to  moist 
conditions,  is  next  in  importance. 

A  fourth  consideration  should  be  the  reliability  of  the  company 
manufacturing  it.  Repairs  and  service  should  be  available  within 
reasonable  distances. 

It  is  well  to  make  use  of  the  manufacturer's  services  for  any 
specific  problem  which  may  present  itself. 

Motor  Troubles. — It  is  impossible  in  a  publication  of  this  type  to 
cover  each  trouble  for  each  particular  type  of  motor,  and  therefore 
they  will  be  discussed  only  generally.  Trouble  with  motors  is  usually 
shown  by  one  of  the  following  manifestations. 


14  CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE  [ClRC.  14 

Failure  to  start  may  be  caused  by  lack  of  proper  voltage,  blown 
fuses,  broken  wires,  too  great  loads,  improper  connections,  a  starting 
device  which  is  out  of  order,  a  switch  not  entirely  closed,  or  improper 
brush  setting. 

Overheating  may  be  caused  by  overloading,  low  voltage,  high  volt- 
age, poor  connections,  worn  or  poorly  lubricated  bearings,  short- 
circuits,  grounds,  lack  of  ventilation,  low  power-factor,  or  a  burned- 
out  fuse. 

Burning  out  of  fuses  may  be  caused  by  overloading,  tight  belts,  low 
voltage,  grounds,  short  circuits,  or  any  of  the  troubles  given  under 
overheating. 

Sparking  at  the  commutator  may  be  due  to  dirty,  worn,  or  poorly- 
fitting  commutator  and  brushes ;  to  improper  setting  of  brush-holder ; 
or  to  grounds,  shorts,  or  open  circuits  within  the  rotor  winding. 

Lack  of  power  may  result  from  low  voltage,  poor  connections,  worn 
or  dry  bearings,  one  fuse  out  on  a  two  or  three-phase  motor,  or  to 
too  tight  a  belt. 

Testing  and  Repair-  of  Motors. — Some  of  the  more  common  methods 
of  testing  and  repairing  are  given  below.  Before  working  on  electric 
circuits  always  turn  off  the  power  at  the  main  switch  before  attempt- 
ing to  touch  the  "live"  parts.  It  may  even  be  desirable  to  remove 
the  fuses  in  exceptional  cases,  to  prevent  unauthorized  persons  from 
turning  on  the  power  while  work  is  being  done  on  the  system. 

Standing  on  a  dry  board  or  rubber  mat,  together  with  the  use  of 
rubber  gloves,  will  minimize  the  danger  of  shock.  Ordinary  rubbers 
or  rubber  boots  on  the  feet  will  also  tend  to  prevent  shocks.  Severe 
shocks  are  caused  by  the  current  flowing  through  one's  body,  and  the 
current  will  not  flow  unless  the  body  is  connected  to  both  sides  of 
the  circuit  at  the  same  time.  It  should  be  remembered  that  the  ground 
as  well  as  the  wire  may  form  one  side  of  the  circuit. 

Play  safe  turn  off  the  power  at  the  main  switch  before  attempting 
to  work  on  the  system. 

A  trouble  lamp  connected  to  the  motor  winding  as  shown  in  the 
diagram,  figure  6,  will  light  if  there  is  a  ground. 

Water  soaked  motors  usually  show  grounds,  as  indicated  above, 
and  must  be  dried  out  before  they  will  operate  properly.  Three 
common  methods  of  drying  are  employed.  The  first  method  is  to 
place  the  motor  in  an  oven  and  bake  it  for  twelve  hours  at  a  tem- 
perature of  150°F,  or  to  hang  it  above  a  gas  jet  for  the  required  length 
of  time  in  order  to  allow  it  to  become  heated  sufficiently  to  evaporate 
the  moisture. 


1927 


ELECTRICAL  EQUIPMENT   USED  IN   DAIRY   MANUFACTURING 


15 


The  second  method  is  to  block  the  rotor   and  apply   a  reduced 

voltage  to  the  motor  terminals,  allowing  the  heat  which  is  generated 

to  dry  the  motor.     This  method  is  used  on  large  motors,  which  are 

difficult   to   move.      It   requires   close   attention   on   the   part   of   the 

operator  to  prevent  excessive  heating  and  the  burning  out  of  the 

motor. 

/^\^^Troub\e   lamp 

vr 

IIOV. 


Moior  terminals 


Fig.  6. — Testing  for  ground.     Lamp  will  light  if  motor  winding  is  grounded. 


Fig.  7. 


Fig.  8. 


Fig.  7. 


-Measuring  the  stator-rotor  clearance  of  a  motor.     The  sectional  model 
shown  in  the  cut  is  for  demonstration  use  only. 

Fig.  8. — Removing  bearing  sleeves. 


A  third  method  is  to  blow  heated  air  through  the  motor  by  means 
of  a  fan. 

Bearings  of  electric  motors  are  of  two  general  types,  those  using 
balls  or  rollers  and  those  using  the  plain  sleeve. 

When  bearings  become  worn,  there,  is  danger  of  the  rotor  rubbing 
on  the  stationary  part,  and  for  this  reason,  the  clearance  between 
rotor  and  stator  should  be  measured  occasionally.  This  is  done  by 
inserting  a  thin,  tapering  gauge  through  slots  provided  in  the  end 
bells    of   the    motor.      The    accompanying   cut,    figure    7,    shows   the 


16  CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE  [ClRC.  14 

method.  The  clearance  should  be  practically  the  same  on  top  and 
bottom  and  on  each  side  of  the  motor. 

The  ball-bearing  assembly  can  usually  be  removed  by  loosening  the 
retaining  bolts,  and  then  driving  it  out  with  a  wooden  block  and 
mallet.  Care  should  be  taken  in  replacing  the  bearing  sleeve  to  drive 
straight,  as  otherwise  it  may  become  sprung  out  of  shape. 

Bearings  of  plain  type  usually  employ  a  ring  oiler.  Before  an 
attempt  is  made  to  drive  out  the  sleeve,  it  is  necessary  to  loosen  the 
retaining  screw  and  also  to  lift  up  the  oil  ring  so  that  it  does  not  catch 
on  the  sleeve  holder.  Figure  8,  illustrates  the  method  of  removal  of 
sleeve  type  bearings. 

The  care  of  brushes  and  commutators  consists  mostly  of  keeping 
them  clean  and  well  fitted. 

Cleaning  is  accomplished  by  brushing  with  a  soft  brush  and  gaso- 
line. If  the  commutator  is  rough,  it  may  be  smoothed  by  holding  a 
piece  of  fine  "00"  sandpaper  against  it  by  means  of  a  block,  while  the 
rotor  is  turned  or  by  placing  it  in  a  lathe  and  taking  a  very  light  cut. 
This  latter  procedure  is  recommended  if  the  commutator  is  out  of 
round  or  is  badly  pitted. 

After  the  commutator  is  smoothed  off,  the  brushes  may  be  fitted 
to  it  by  placing  a  band  of  "00"  sandpaper  around  the  commutator, 
rough  side  out,  in  contact  with  the  brushes,  and  rocking  the  com- 
mutator and  sandpaper  back  and  forth. 

The  mica  used  for  insulating  one  section  of  the  commutator  from 
another,  sometimes  projects  above  the  surface  and  causes  sparking. 
It  should  be  cut  down  so  that  its  edge  is  below  the  surface.  This  is 
best  accomplished  by  means  of  an  undercutting  machine  or  on  a  lathe, 
but  may  be  done  in  an  emergency  with  a  broken  hack-saw  blade,  which 
has  been  ground  off  to  the  required  thickness. 

A  commutator  should  have  a  smooth,  glassy,  chocolate  brown 
appearance. 

Centrifugal  switches  on  split-phase  motors  may  have  corroded  or 
burned  points  and  an  occasional  smoothing  and  brightening  will  aid 
in  keeping  them  in  good  working  order. 

Lubrication  of  Motors. — The  lubrication  of  electric  motors  calls 
for  a  light,  free-flowing  mineral  oil,  which  can  work  in  between  sur- 
faces where  there  is  small  clearance.  A  dynamo  oil  or  medium  auto 
oil  is  satisfactory.  Large  motors  may  use  a  heavier-bodied  oil.  Ball- 
bearing motors  use  a  specially  prepared  grease  or  vaseline.  It  is  very 
desirable  to  have  a  regular  schedule  for  inspection  and  lubrication 
of  bearings. 


1927]        ELECTRICAL  EQUIPMENT   USED  IN   DAIRY   MANUFACTURING  17 


LIGHTING 

Proper  Illumination. — Good  illumination  may  be  denned  as  a 
uniform,  non-glaring  light,  free  from  shadows  and  of  sufficient  inten- 
sity that  the  work  may  not  be  handicapped.  The  best  light  for  all 
except  cold  storage  rooms  is  sunlight ;  for  this  reason,  provision  for 
an  abundance  of  natural  light  through  windows  or  sky  lights  is 
recommended. 

Sufficient  light  is  conductive  to  more  efficient  use  of  labor,  to  better 
health  of  workers,  and  to  more  sanitary  conditions.  The  proper 
intensity  of  artificial  lighting  for  dairy  plants,  as  recommended  by 
illuminating  engineers,  has  been  set  at  a  value  of  four  to  eight-foot 


Fig.  9. — Two  rooms  furnished  the  same  amount  of  light.     Note  degree  of 
illumination  due  to  light  and  dark  colored  walls. 

candles.  A  more  simple  method  of  arriving  at  the  proper  illuminat- 
ing value,  is  to  allow  1.5  to  2.0  watts  lamp  capacity  per  square  foot 
of  floor  area,  with  light  colored  rooms  and  ceilings  of  medium  height. 

Figure  9  illustrates  the  marked  effect  of  the  color  of  walls  upon 
the  lighting  intensity  of  two  rooms,  each  supplied  with  the  same 
amount  of  light.  This  is  of  special  importance  in  refrigeration  rooms, 
where  the  heat  produced  from  the  electric  lamp  causes  loss  of 
refrigeration. 

The. selection  of  the  proper  type  of  fixture  is  of  importance.  For 
factory  conditions,  the  porcelain  enameled  type  of  reflector  has  gen- 
erally been  found  to  be  good ;  it  has  high  powers  of  reflection,  is  not 
fragile,  is  easily  cleaned,  and  is  inexpensive.  The  standard  R.L.M. 
dome  reflector  is  a  good  type.  The  special  moisture  proof  fixture 
with  extra  glass  cover  is  also  good,  under  conditions  of  high  moisture 
or  in  the  presence  of  corroding  vapors. 


18 


CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE 


[ClEC.  14 


TABLE  2 
Effect  of  Voltage  on  Electric  Lamps* 


Lamp 
voltage 

Circuit 
voltage 

Per  cent  normal 
voltage 

Per  cent  normal 
illumination 

Per  cent  normal 
life 

110 

95 

35 

181 

112 

97 

91 

140 

115 

115 

100 

100 

100 

117 

101 

106 

79 

120 

104 

116 

57 

125 

108 

133 

32 

*  Data  supplied  by  National  Lamp  Works— General  Electric  Co. 

Efficiency  of  Electric  Lamps. — The  illuminating  efficiency  of  elec- 
tric lamps  and  the  length  of  life,  are  greatly  affected  by  the  operating 
voltage.  The  normal  life  of  an  electric  lamp  is  1000  hours.  As  shown 
in  Table  6,  the  illuminating  powers  of  a  lamp  are  increased  by  an 
increase  in  the  voltage,  but  at  a  considerable  sacrifice  in  length  of  life. 


Main 


I 


A    k 


Pilot,  light 


7b  motor 

Fig.  10. — Wiring  diagram  for  pilot  light. 

The  Pilot  Light. — There  are  many  places  about  the  creamery 
where  it  is  desirable  to  have  a  signal  for  indicating  when  current  is 
flowing  to  lights  or  equipment  as  reminders  to  the  workmen.  In  many 
plants  considerable  energy  is  wasted  by  failure  to  turn  off  electricity 
at  the  proper  time.     To  overcome  this  trouble  it  is  possible  to  install 


I92?]        ELECTRICAL  EQUIPMENT  USED  IN   DAIRY   MANUFACTURING 


19 


in  a  conspicuous  place  a  pilot  light  of  low  wattage,  such  as  that  shown 
in  the  diagram,  figure  10.  The  lamp  will  always  be  lighted  when  the 
main  switch  is  turned  on. 


HEATING    AND    PROCESSING 

Electrical  energy  is  used  successfully  for  heating  where  it  is  not 
too  expensive,  where  it  saves  a  considerable  amount  of  labor,  and 
where  it  offers  better  control  of  temperature  than  other  methods.     It 


Fig.  11.  Fig.  12. 

Fig.  11. — Home-made  open  type  electric  heater. 
Fig.  12. — Immersion  type  electric  heater. 

may  require  a  longer  heating  period  than  oil  or  coal,  but  by  proper 
arrangement  of  the  schedule,  it  will  usually  be  found  to  be  sufficiently 
rapid. 

Types  of  Electric  Heaters. — There  are  a  number  of  different  types 
of  heaters  available.  One  is  the  plain  open  resistance  type,  in  which 
resistance  wire  is  wound  around  a  porcelain  or  asbestos  composition 
core,  or  is  merely  stretched  between  insulated  binding  posts  or  grids. 
Another  is  the  immersion  type,  which  is  made  of  a  resistance  wire 
housing.  The  open  type,  figure  11,  is  used  for  heating  air,  while  the 
immersion  type,  figure  12,  is  used  for  heating  liquids.  With  the 
latter  the  current  must  not  be  left  on  when  the  heater  is  not  sub- 
merged, lest  it  burn  out  or  its  life  be  shortened.  With  some  makes, 
it  is  possible  to  renew  the  burned  out  element  at  nominal  cost. 


20 


CALIFORNIA   AGRICULTURAL    EXTENSION    SERVICE 


[Circ.  14 


Some  elements  are  so  connected  that  several  different  heats  may 
be  had  by  adjustment  of  a  switch. 

Cost  of  Electrical  Heating. — The  cost  of  heating  with  electricity  is 
usually  determined  by  the  power  rate  and  the  efficiency  of  the  installa- 
tion. Electric  heating  units  are  100  per  cent  efficient,  and  if  proper 
insulation  is  used  with  them,  a  higher  over-all  efficiency  can  usually 
be  obtained,  taking  all  factors  into  consideration,  than  when  coal  or  oil 
is  used.  From  one  kw-hr.  there  are  produced  3412  B.t.u.,  while  from 
one  pound  of  coal  about  13,000  B.t.u.  are  produced.  (B.t.u. — British 
thermal  unit — is  the  unit  of  heat,  representing  the  amount  of  heat 
necessary  to  raise  one  pound  of  water  1  degree  Fahrenheit.)  The 
following  table  shows  the  comparative  cost  of  energy  alone  for  coal,  oil, 

TABLE  3 
Comparative   Approximate   Cost   of   Heat  Energy   from   Different   Sources 


Cost  per  unit  of  fuel 

Efficiency  of  heater  in  per  cent 
Heat  units  available 

Heat  units  for  $1.00 


Coal 


$10.00  per  ton 

70 

13,000  B.t.u. 

per  lb. 

1,820,000 


Oil 


$2.10  per  bbl. 

72 

18,500  B.t.u. 

per  lb. 

2,125,700 


Electricity 


1.5c  per  kw-hr. 

100 

3,412  B.t.u. 

per  kw-hr. 

227,667 


and  electric  heating.  The  over-all  cost  of  heating  should  include  items 
such  as  labor,  interest  on  investment,  and  depreciation.  Oftentimes 
the  question  of  cleanliness  is  a  factor  that  must  be  considered. 


AUTOMATIC  CONTROL  OF  EQUIPMENT 

Many  operations,  such  as  starting  and  stopping  of  machinery, 
control  of  temperature,  and  processing  in  general,  are  easily  handled 
by  automatic  electrical  control.  One  of  the  advantages  is  that  of  being 
able  to  control  from  a  distance. 

The  controlling  mechanism  may  operate  from  a  combination  of  a 
thermostat  which  operates  by  temperature  change ;  from  a  pressure 
switch  which  operates  from  changes  of  pressure  and  from  a  time 
switch  which  operates  from  changes  of  time.  It  may  also  operate 
from  any  one  of  the  above.  The  relay  is  used  where  large  currents 
are  to  be  handled.  Magnetic  valves,  such  as  shown  in  figure  13,  are 
used  for  handling  liquids  and  gases.  Magnetic  switches  may  be  con- 
trolled by  means  of  a  push  button  station,  located  some  distance  from 
the  switch.  This  makes  possible  a  saving  in  wire,  and  enables  the 
switch  box  to  be  installed  in  a  dry  place  on  the  wall. 


1927]        ELECTRICAL  EQUIPMENT  USED  IN   DAIRY   MANUFACTURING 


21 


r>c-> 


Fig.  13. — Magnetic  value  used  for  controlling  the  flow  of  liquids  such  as  brine  or 
water  passing  through  pipe  lines.     (Courtesy  Taylor  Instrument  Co.) 


ELECTRIC   WIRING 

Wiring  Regulations.3 — The  safety  regulations  of  cities  and  states 
require  that  certain  conditions  be  complied  with  in  the  installation  of 
electrical  wiring,  and  these  should  always  be  consulted  before  laying 
out  a  piece  of  work.  Care  should  be  taken  not  to  overload  small  lines 
by  attaching  large  electrical  appliances  to  them.  Continued  over- 
loading will  cause  heating  and  gradual  failure  of  the  insulation. 

Wires  should  be  large  enough  to  carry  a  considerable  overload 
without  heating  and  without  causing  serious  voltage  drop.  Rubber 
covered  wire  is  used  for  inside  and  weatherproof  for  outside  work. 
The  latter  is  much  more  brittle  and  more  difficult  to  bend.  Rubber 
covered  wire  with  white  or  striped  covering  may  be  secured,  and  has 
the  advantage  of  being  easily  traced  as  one  side  of  a  circuit,  if  black 
wire  is  used  for  the  other  side.  It  is  also  cleaner  to  handle  than  the 
black  wire. 

All  wiring  should  be  in  metal  conduit  or  pipe.  The  rigid  type 
should  be  used  in  creameries  where  possible,  because  it  is  more  nearly 
waterproof  than  is  the  flexible.  The  latter  type  is  often  used  for 
temporary  rewiring  work,  or  for  installation  where  there  is  small 
danger  of  water  collecting,  or  where  it  is  difficult  to  bend  the  rigid 
type  to  the  proper  shape.  The  armored  cable  figure  14,  having  one, 
two,  or  three  conductors  is  very  often  used  for  temporary  lines,  or  on 
portable  machines,  such  as  tube  cleaners,  or  ice  stackers.     In  connec- 

3  See  Industrial  Accident  Commission  of  the  State  of  California.  Electric 
safety  orders.    1925  ed.,  California  State  Printing  Office,  Sacramento,  Calif.    1925. 


22  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [ClRC.  14 

tion  with  the  proper  kind  of  plugs  or  quick  attachment  devices,  this 
cable  is  very  convenient.  Flexible  cords  having  one,  two,  or  three 
conductors  are  also  used  in  connection  with  portable  machinery. 

Electrical  Connections. — Good  electrical  connections  are  important 
from  the  standpoint  of  safety  and  reliability,  if  one  is  to  have  the  best 
service  from  his  electrical  equipment.  They  should  be  large  enough 
to  carry  the  load  safely,  should  be  well  insulated,  and  should  have 
sufficient  mechanical  strength  not  to  sag  or  break. 


I 


%4 


i 


C  D 


Fig.   14. — A,  flexible  armored  cable.     B,  flexible  conduit.     C,   lugs. 
D,  tubular  connectors. 

All  connections  should  be  well  bolted  together  or  soldered.  All 
bolted  connections  should  be  made  with  copper  lugs  (fig.  14),  soldered 
to  the  ends  of  the  wires  and  then  bolted  together.  Temporary  con- 
nections can  be  made  very  satisfactorily  with  tubular  connectors 
(fig.  14).     The  tightening  of  screws  holds  the  wire  firmly  in  place. 

The  insulation  should  consist  of  first  a  layer  of  rubber  insulating 
tape  wound  on  the  half-lap ;  second,  a  layer  of  friction  tape,  also 
wound  on  the  half-lap ;  third,  a  coat  of  good  insulating  paint  to  give  a 
desirable  finish,  and  make  the  connection  waterproof. 

Switches  and  Starters. — The  simplest  starting  device  is  a  plain, 
enclosed,  single-throw  switch,  with  an  externally-operated  handle  for 
throwing  it  off  and  on.  This  switch  is  sometimes  made  in  the  double- 
throw  type  with  one  set  of  fuses  for  starting,  and  another  for  running. 
The  latter  type  of  construction  is  preferable  because  it  gives  the  motor 
better  protection,  if  small  fuses  are  used  on  the  ''running"  side. 

The  magnetic  switch  is  made  to  be  operated  from  a  push  button 
station  or  by  a  hand-operated  lever.     This  type  of  switch  has  the 


1927]        ELECTRICAL  EQUIPMENT  USED  IN  DAIRY   MANUFACTURING  23 

advantage  that  it  automatically  opens  the  circuit  when  the  power  goes 
off  or  the  voltage  becomes  too  low.  A  thermal  overload  relay  or  a 
magnetic  relay  is  used  for  protection  of  the  motor  from  overloads. 

Where  motors  larger  than  7%  hp.*  are  used,  it  is  customary  to  use 
a  starter  with  a  small  transformer  or  resistance  built  in.  This  starter 
serves  to  reduce  the  voltage  applied  to  the  motor  and  thus  prevents  an 
excessive  current  being  drawn  from  the  line. 


FUSING   AND   PROTECTION   OF   CIRCUITS 

The  proper  fusing  of  electric  lines  is  of  great  importance,  for  the 
fuse  is  to  the  electric  line,  what  the  safety  plug  is  to  the  steam  boiler. 
A  fuse  contains  a  small  strip  of  metal,  which  melts  out  when  a  cur- 
rent greater  than  its  rating  in  amperes  is  passed  through  it.  This 
breaks  the  circuit  and  stops  the  flow  of  electricity.     The  practice  of 


Mg.  15. — Common  types  of  fuses.     A,  plug;  B,  cartridge;  C,  time-limit; 
D,  renewable  cartridge. 

"bridging"  burned  out  fuses  with  pennies  or  nails  or  wires  is  very 
dangerous,  and  may  be  compared  to  that  of  substituting  a  steel  plug 
in  the  place  of  a  fusible  plug  in  a  steam  boiler.  The  protection  is 
gone,  and  the  result  may  be  a  burned  out  motor,  a  burned  out  line, 
or  possibly  a  fire. 

Types  of  Fuses. — Four  types  of  fuses,  as  shown  in  figure  15  are 
ordinarily  used  on  motor  and  lighting  circuits.  The  one  marked  A  is 
the  ordinary  plug  fuse,  which  is  used  mostly  in  lighting  circuits, 
and  is  made  in  sizes  up  to  30  amperes.  B  is  the  plain  cartridge,  such 
as  is  used  on  lighting  and  motor  circuits,  in  sizes  up  to  400  amperes 
or  more.  C  is  a  time-limit  fuse,  which  is  used  mainly  on  motor  cir- 
cuits. While  this  fuse  will  not  burn  out  on  a  momentary  overload 
like  the  ordinary  fuse,  if  the  overload  continues  for  considerable 
time,  it  will  burn  out  and  protect  the  motor.  The  fuse  is  easily 
renewed  by  replacing  a  small  link.  D  is  a  renewable-link  cartridge 
fuse,  which  has  practically  the  same  characteristics  as  the  plain  cart- 


*  See  Double  wound  squirrel  cage  motor,  page  8. 


24  CALIFORNIA   AGRICULTURAL   EXTENSION    SERVICE  [ClRC.  14 

ridge  fuse.  It  has  the  advantage  also  of  having  a  renewable  link, 
which  when  burned  out,  can  be  replaced  at  a  nominal  cost. 

Fuses  should  be  of  such  a  size  or  amperage  that  they  will  carry  no 
more  than  the  maximum,  safe,  carrying  capacity  in  amperes  of  the 
line,  motor,  or  device  which  is  to  be  protected.  Extra  long  fuses  are 
used  on  lines  operating  at  440  volts  or  above. 

There  are  special  conditions  which  must  be  overcome  by  fuses 
selected  for  motors.  The  latter  draw  for  only  a  short  time,  a  starting 
current  so  heavy  that  it  would  burn  out  a  fuse  small  enough  to  afford 
protection  against  a  continuous  running  overload.  If  plain  fuses  are 
used,  two  sets  are  usually  installed,  one  of  about  200%  of  the  motor 


Fig.  16. — Thermal  over-load  relay.     (Courtesy  General  Electric  Co.) 

name  plate  amperage  for  starting,  and  another  of  from  115  to  125% 
of  name  plate  amperage  for  running.  If  time  limit  fuses  are  used, 
they  are  usually  of  about  110%  of  the  name  plate  amperage  of  the 
motor.  For  example,  if  a  motor  used  15  amperes  of  current  at  full 
load,  the  fuse  should  be  110%  of  15  amperes,  or  16.5.  The  nearest 
commercial  size  should  be  used. 

Types  of  Relays. — Overload-relays  are  electrical  devices,  which 
take  the  place  of  fuses  in  the  motor  circuit.  They  are  of  two  general 
types.  The  thermal  overload-relay,  figure  16,  opens  the  motor  circuit, 
by  means  of  a  small  blade,  made  of  two  dissimilar  metals,  and  which 
bends  to  one  side  when  heated  by  the  current  to  a  certain  predeter- 
mined temperature.    It  is  reset  by  pushing  a  trip  or  plunger. 

The  magnetic  overload-relay  opens  the  circuit  by  the  action  of  a 
plunger,  which  is  raised  by  the  pull  of  a  magnet,  when  the  prede- 
termined current  value  is  exceeded. 

The  adjustment  of  the  relay  is  important,  as  is  also  the  keeping  of 
oil  in  the  dashpot.  Magnetic  overload  relays  should  be  adjusted  to 
operate  at  about  115  to  125%  of  the  name  plate  amperage  of  the 
motor. 


1927]        ELECTRICAL  EQUIPMENT  USED  IN  DAIRY  MANUFACTURING  25 


POWER  TRANSMISSION 

Types  of  Drive. — The  most  common  methods  of  drive  are  by  direct 
connection  to  the  motor  shaft,  or  by  silent  chain  drive,  belt,  friction, 
or  gears.  No  one  method  can  be  said  to  be  best  for  all  conditions,  as 
the  size  and  nature  of  the  load,  as  well  as  sanitary  considerations,  may 
influence  the  selection  of  a  particular  method. 

In  general,  the  elimination  of  belts  and  chains  which  throw  oil 
and  dirt  about  a  creamery  is  desirable  from  the  standpoint  of  cleanli- 
ness. A  gear  set  or  enclosed  chain  running  in  oil  is,  next  to  the  direct- 
connected  unit,  the  most  desirable.  There  are  places  where  there  is 
plenty  of  space  for  a  belt  drive,  and  where  the  ease  of  installation 
justifies  its  use.  If  certain  heavy  loads  must  be  carried,  a  belt  will 
slip  and  protect  the  machine  or  motor  from  possible  injury  in  starting 
or  at  peak  loads. 

There  is  considerable  controversy  over  the  question  of  group  and 
individual  drives.  The  group  drive  is  lower  in  the  first  cost,  and  if  a 
certain  group  of  machines  are  always  operated  at  the  same  time,  it  is 
often  the  logical  method.  However,  there  is  the  disadvantage  of  hav- 
ing line  shafts  and  counter  shafts,  which  must  be  considered  from  the 
sanitary  standpoint,  as  well  as  that  of  safety.  If  a  machine  is  operated 
alone,  it  is  better  to  use  individual  drive. 

Adjustment  of  Drive. — There  is  considerable  importance  attached 
to  the  adjustment  of  any  form  of  drive.  Chains  must  be  kept  neither 
too  tight  nor  too  loose,  or  they  will  wear  and  consume  power  needlessly. 
Gears  and  belts  must  be  run  under  the  same  conditions.  Tight  belts 
place  a  great  strain  upon  bearings.  The  short  center  belt  drive  with 
idler  is  gaining  in  popularity  and  gives  very  good  service,  at  the  same 
time  conserving  floor  space. 

The  proper  alignment  of  pulleys  is  important.  Belts  which  are 
held  in  place  by  guides,  sticks,  or  any  other  such  means  are  wasteful 
of  power  and  wear  rapidly. 

Leather  belts  may  be  kept  soft  and  pliable  by  frequent  applications 
of  a  small  amount  of  neatsfoot  oil,  while  other  types  of  belts  require  a 
special  dressing,  recommended  by  the  manufacturer. 

Speed  of  Pulleys  and  Gears. — The  speed  of  pulleys  and  gears  may 
be  calculated  as  follows:  Diameter  of  Driver  (inches)  X  R.P.M.  = 
Diameter  of  Driven  (inches)   X  R.P.M. 


26  CALIFORNIA    AGRICULTURAL   EXTENSION    SERVICE  [ClBC.  14 

(a)  Diameter  of  driver  multiplied  by  its  R.P.M.,  divided  by 
diameter  of  driven,  gives  K.P.M.  of  driven. 

(b)  Diameter  of  driver  multiplied  by  its  R.P.M.,  divided  by  R.P.M. 
of  driven,  gives  diameter  of  driven. 

(c)  In  the  case  of  gears,  the  same  general  formula  may  be  used, 
by  substituting  the  number  of  teeth  in  the  place  of  "Diameter"  in  the 
formula. 

Problem : 
Given : 

A  pulley  ten  inches  in  diameter  and  having  a  speed  of  100 
R.P.M.  drives  a  second  pulley  at  200  R.P.M.     Find  the  diameter 
of  the  second  pulley. 
Solution : 

Use  formula  (b)  as  shown  above.  Diameter  of  driver  times  its 
diameter  in  inches,  divided  by  R.P.M.  of  driven  equal  diameter  of 
driven. 

100  X  10  -f-  200  =  5. 
Therefore,  the  diameter  of  the  driven  pulley  must  be  5  inches. 


PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


No. 

275.  The     Cultivation     of     Belladonna     in 

California. 

276.  The  Pomegranate. 

277.  Sudan    Grass. 

278.  Grain    Sorghums. 

279.  Irrigation   of  Rice   in    California. 
283.  The  Olive  Insects  of  California. 
294.   Bean    Culture  in    California. 

304.  A  Study  of  the  Effects  of  Freezes  on 

Citrus    in    California. 
310.   Plum    Pollination. 
312.  Mariout  Barley. 
813.   Pruning      Young      Deciduous      Fruit 

Trees. 
319.  Caprifigs    and    Caprification. 

324.  Storage  of   Perishable  Fruit  at  Freez- 

ing Temperatures. 

325.  Rice      Irrigation      Measurements      and 

Experiments    in    Sacramento   Valley, 

1914-1919. 
328.   Prune    Growing   in    California. 
331.   Phylloxera-Resistant    Stocks. 
335.   Cocoanut    Meal    as    a    Feed    for    Dairy 

Cows   and    Other   Livestock. 

339.  The    Relative    Cost    of    Making    Logs 

from    Small   and   Large  Timber. 

340.  Control     of     the     Pocket     Gopher     in 

California. 

343.  Cheese    Pests    and    Their    Control. 

344.  Cold    Storage   as   an   Aid   to   the   Mar- 

keting of  Plums. 

346.  Almond    Pollination. 

347.  The  Control  of  Red  Spiders  in  Decid- 

uous Orchards. 

348.  Pruning  Young  Olive  Trees. 

349.  A     Study    of    Sidedraft    and    Tractor 

Hitches. 

350.  Agriculture      in      Cut-over      Redwood 

Lands. 

352.  Further  Experiments  in  Plum  Pollina- 
tion. 

853.   Bovine   Infectious   Abortion. 

354.   Results  of  Rice  Experiments  in    1922. 

357.  A  Self-mixing  Dusting  Machine  for 
Applying  Dry  Insecticides  and 
Fungicides. 

858.  Black  Measles,  Water  Berries,  and 
Related  Vine  Troubles. 

361.  Preliminary   Yield   Tables    for    Second 

Growth   Redwood. 

362.  Dust  and  the  Tractor  Engine. 

363.  The  Pruning  of  Citrus  Trees  in   Cali- 

fornia. 

364.  Fungicidal    Dusts    for    the    Control    of 

Bunt. 

365.  Avocado  Culture  in   California. 

366.  Turkish  Tobacco  Culture,   Curing  and 

Marketing. 

367.  Methods  of  Harvesting  and  Irrigation 

in   Relation   of  Mouldy   Walnuts. 

368.  Bacterial  Decomposition  of  Olives  dur- 

ing  Pickling. 

369.  Comparison      of     Woods      for     Butter 

Boxes. 

370.  Browning  of  Yellow  Newtown  Apples. 

371.  The    Relative    Cost   of    Yarding    Small 

and   Large   Timber. 

372.  The  Cost  of  Producing  Market  Milk  and 

Butterfat  on  246  California  Dairies. 

373.  Pear   Pollination. 

374.  A   Survey  of  Orchard  Practices  in  the 

Citrus    Industry  of    Southern     Cali- 
fornia. 

375.  Results   of   Rice   Experiments   at   Cor- 

tena,    1923. 

376.  Sun-Drying  and  Dehydration   of  Wal- 

nuts. 

377.  The   Cold   Storage   of   Pears. 

379.  Walnut   Culture    in    California. 

380.  Growth    of    Eucalyptus    in    California 

Plantations. 

381.  Growing     and     Handling     Asparagus 

Crowns. 


BULLETINS 
No. 


382. 

383. 

385. 
386. 

387. 
388. 

389. 
390. 

391. 

392. 
393. 
394. 

395. 


397. 


398. 
399. 


400. 
401. 

402. 
403. 
404. 
405. 
406. 
407. 


408. 
409. 


410. 


411. 
412. 


413. 


414. 


415. 

416. 


417. 


411 


419. 
420. 


421. 
422. 


423. 
424. 


425. 
426. 


427. 


•12; 


Pumping  for  Drainage  in  the  San 
Joaquin    Valley,    California. 

Monilia  Blossom  Blight  (Brown  Rot) 
of  Apricot. 

Pollination    of    the    Sweet    Cherry. 

Pruning  Bearing  Deciduous  Fruit 
Trees. 

Fig   Smut. 

The  Principles  and  Practice  of  Sun- 
drying  Fruit. 

Berseem  or   Egyptian    Clover. 

Harvesting  and  Packing  Grapes  in 
California. 

Machines  for  Coating  Seed  Wheat  with 
Copper    Carbonate   Dust. 

Fruit    Juice    Concentrates. 

Crop  Sequences  at  Davis. 

Cereal  Hay  Production  in  California. 
Feeding  Trials  with  Cereal  Hay. 

Bark   Diseases   of   Citrus   Trees. 

The  Mat  Bean  (Phaseolus  aconitifo 
lius). 

Manufacture  of  Roquefort"  Type  Cheese 
from    Goat's   Milk. 

Orchard  Heating  in  California. 

The  Blackberry  Mite,  the  Cause  of 
Redberry  Disease  of  the  Himalaya 
Blackberry,    and    its    Control. 

The  Utilization  of  Surplus  Plums. 

Cost  of  Work  Horses  on  California 
Farms. 

The  Codling  Moth  in  Walnuts. 

Farm-Accounting  Associations. 

The  Dehydration  of  Prunes. 

Citrus  Culture  in  Central  California. 

Stationary  Spray  Plants  in  California. 

Yield,  Stand  and  Volume  Tables  for 
White  Fir  in  the  California  Pine 
Region. 

Alternaria  Rot  of  Lemons. 

The  Digestibility  of  Certain  Fruit  By- 
products as  Determined  for  Rumi- 
nants. 

Factors  Affecting  the  Quality  of  Fresh 
Asparagus  after  it  is  Harvested. 

Paradichlorobenzene  as  a  Soil  Fumi- 
gant. 

A  Study  of  the  Relative  Values  of  Cer- 
tain Root  Crops  and  Salmon  Oil  as 
Sources  of  Vitamin  A  for  Poultry. 

The  California  Poultry  Industry;  a 
Statistical   Study. 

Planting  and  Thinning  Distances  for 
Deciduous  Fruit  Trees. 

The  Tractor  on  California  Farms. 

Culture  of  the  Oriental  Persimmon 
in    California. 

Poultry  Feeding:  Principles  and 
Practice. 

A  Study  of  Various  Rations  for 
Finishing  Range  Calves  as  Baby 
Beeves. 

Economic  Aspects  of  the  Cantaloupe 
Industry. 

Rice  and  Rice  By-products  as  Feeds 
for   Fattening    Swine. 

Beef   Cattle   Feeding   Trials,    1921-24. 

Cost  of  Producing  Almonds  in  Cali- 
fornia;  a  Progress  Report. 

Apricots  (Series  on  California  Crops 
and  Prices). 

The  Relation  of  Rate  of  Maturity  to 
Egg  Production. 

Apple    Growing   in    California. 

Apple     Pollination     Studies     in 
fornia. 

The  Value  of  Orange  Pulp  for  Milk 
Production. 

The     Relation     of     Maturity     of     Cali- 
fornia     Plums      to      Shipping 
Dessert   Quality. 


Cali- 


and 


No. 

87.  Alfalfa. 
117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant. 
127.  House   Fumigation. 
129.  The  Control  of  Citrus   Insects. 
136.   Melilotus    indica    as    a    Green-Manure 

Crop  for  California. 
144.   Oidium    or    Powdery    Mildew    of    the 

Vine. 
157.  Control  of  the  Pear  Scab. 
160.  Lettuce  Growing  in  California. 
164.   Small  Fruit  Culture  in  California. 
166.  The  County   Farm  Bureau. 
170.   Fertilizing     California     Soils    for    the 

1918   Crop. 
173.  The    Construction    of    the    Wood-Hoop 

Silo. 

178.  The   Packing  of  Apples   in   California. 

179.  Factors    of    Importance   in    Producing 

Milk  of  Low  Bacterial  Count. 
190.  Agriculture  Clubs  in  California. 
199.   Onion    Growing   in    California. 

202.  County    Organizations   for   Rural    Fire 

Control. 

203.  Peat   as   a   Manure   Substitute. 

209.  The  Function  of  the  Farm   Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.   Salvaging    Rain-Damaged    Prunes. 
215.    Feeding  Dairy  Cows  in  California. 
217.  Methods   for  Marketing  Vegetables   in 

California. 
220.   Unfermented   Fruit   Juices. 
228.   Vineyard   Irrigation  in  Arid  Climates. 

230.  Testing  Milk,    Cream,   and   Skim   Milk 

for  Butterfat. 

231.  The    Home    Vineyard. 

232.  Harvesting    and    Handling    California 

Cherries    for    Eastern    Shipment. 

234.  Winter  Injury  to  Young  Walnut  Trees 

during  1921-22. 

235.  Soil     Analysis     and     Soil     and     Plant 

Inter-relations. 

236.  The    Common     Hawks    and    Owls    of 

California    from    the    Standpoint    of 
the  Rancher. 

237.  Directions  for  the  Tanning  and  Dress- 

ing of  Furs. 

238.  The  Apricot  in   California. 

239.  Harvesting     and     Handling     Apricots 

and  Plums  for  Eastern   Shipment. 

240.  Harvesting    and    Handling    Pears    for 

Eastern   Shipment. 

241.  Harvesting  and  Handling  Peaches  for 

Eastern   Shipment. 

243.  Marmalade  Juice  and  Jelly  Juice  from 

Citrus  Fruits. 

244.  Central  Wire  Bracing  for  Fruit  Trees. 

245.  Vine   Pruning  Systems. 

247.  Colonization    and    Rural   Development. 

248.  Some   Common    Errors    in    Vine  Prun- 

ing and  Their  Remedies. 

249.  Replacing    Missing    Vines. 

250.  Measurement   of   Irrigation   Water   on 

the  Farm. 

252.  Supports  for  Vines. 

253.  Vineyard  Plans. 

254.  The  Use  of  Artificial  Light  to  Increase 

Winter   Egg    Production. 


CIRCULARS 
No. 
255. 


256. 
257. 
258. 
259. 
261. 
262. 
263. 
264. 

265. 
266. 

267. 

269. 
270. 
272. 

273. 
274. 

276. 
277. 

278. 

279. 

281. 

282. 

283. 
284. 
285. 
286. 
287. 
288. 
289. 
290. 
291. 

292. 
293. 
294. 
295. 

296. 

298. 

299. 
300. 
301. 
302. 
303. 

304. 
305. 
306. 

307. 
308. 
309. 


Leguminous  Plants  as  Organic  Fertil- 
izer   in    California    Agriculture. 

The   Control   of   Wild   Morning   Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning   Deciduous   Fruits. 

Pear  By-products. 

Sewing  Grain  Sacks. 

Cabbage  Growing  in   California. 

Tomato  Production  in   California. 

Preliminary  Essentials  to  Bovine 
Tuberculosis  Control. 

Plant   Disease   and   Pest   Control. 

Analyzing  the  Citrus  Orchard  by 
Means   of   Simple   Tree   Records. 

The  Tendency  of  Tractors  to  Rise  in 
Front;    Causes   and   Remedies. 

An  Orchard  Brush  Burner. 

A  Farm  Septic  Tank. 

California  Farm  Tenancy  and  Methods 
of  Leasing. 

Saving  the  Gophered   Citrus  Tree. 

Fusarium  Wilt  of  Tomato  and  its  Con- 
trol by  Means  of  Resistant  Varieties. 

Home  Canning. 

Head,  Cane,  and  Cordon  Pruning  of 
Vines. 

Olive  Pickling  in  Mediterranean  Coun- 
tries. 

The  Preparation  and  Refining  of  Olive 
Oil   in    Southern    Europe. 

The  Results  of  a  Survey  to  Determine 
the  Cost  of  Producing  Beef  in  Cali- 
fornia. 

Prevention  of  Insect  Attack  on  Stored 
Grain. 

Fertilizing  Citrus  Trees  in   California. 

The   Almond    in    California. 

Sweet  Potato  Production  in  California. 

Milk  Houses  for  California  Dairies. 

Potato   Production    in    California. 

Phylloxera  Resistant  Vineyards. 

Oak  Fungus  in  Orchard  Trees. 

The  Tangier  Pea. 

Blackhead  and  Other  Causes  of  Loss 
of  Turkeys  in   California. 

Alkali   Soils. 

The    Basis    of    Grape    Standardization. 

Propagation    of   Deciduous    Fruits. 

The  Growing  and  Handling  of  Head 
Lettuce  in   California. 

Control  of  the  California  Ground 
Squirrel. 

The  Possibilities  and  Limitations  of 
Cooperative   Marketing. 

Poultry   Breeding   Records. 

Coccidiosis  of  Chickens. 

Buckeye  Poisoning  of  the  Honey  Bee. 

The   Sugar   Beet   in   California. 

A  Promising  Remedy  for  Black  Measles 
of  the  Vine. 

Drainage  on  the  Farm. 

Liming  the  Soil. 

A  General  Purpose  Soil  Auger  and  its 
Use  on  the  Farm. 

American    Foulbrood   and  its   Control. 

Cantaloupe  Production   in   California. 

Fruit  Tree  and   Orchard  Judging. 


The  publications  listed  above  may  be  had  by  addressing 

College  of  Agriculture, 

University  of  California, 

Berkeley,  California, 

12m-9,'27 


